﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.ApplicationModel;
using Windows.ApplicationModel.Activation;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Core;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls.Primitives;
using Microsoft.UI.Xaml.Data;
using Microsoft.UI.Xaml.Input;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Navigation;
using Xamarin.Forms;
using Application = Microsoft.UI.Xaml.Application;
using Frame = Microsoft.UI.Xaml.Controls.Frame;
using NavigationEventArgs = Microsoft.UI.Xaml.Navigation.NavigationEventArgs;

namespace Embedding.UWP
{
	/// <summary>
	/// Provides application-specific behavior to supplement the default Application class.
	/// </summary>
	sealed partial class App : Application
	{
		/// <summary>
		/// Initializes the singleton application object.  This is the first line of authored code
		/// executed, and as such is the logical equivalent of main() or WinMain().
		/// </summary>
		public App()
		{
			this.InitializeComponent();
			this.Suspending += OnSuspending;
		}

		/// <summary>
		/// Invoked when the application is launched normally by the end user.  Other entry points
		/// will be used such as when the application is launched to open a specific file.
		/// </summary>
		/// <param name="e">Details about the launch request and process.</param>
		protected override void OnLaunched(LaunchActivatedEventArgs e)
		{
#if DEBUG
            if (System.Diagnostics.Debugger.IsAttached)
            {
                //this.DebugSettings.EnableFrameRateCounter = true;
            }
#endif
			Frame rootFrame = Window.Current.Content as Frame;

			// Do not repeat app initialization when the Window already has content,
			// just ensure that the window is active
			if (rootFrame == null)
			{
				// Create a Frame to act as the navigation context and navigate to the first page
				rootFrame = new Frame();

				rootFrame.NavigationFailed += OnNavigationFailed;
				rootFrame.Navigated += OnNavigated;

				Forms.Init(e);

				if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
				{
					//TODO: Load state from previously suspended application
				}

				// Place the frame in the current Window
				Window.Current.Content = rootFrame;

				// Register a handler for BackRequested events and set the
				// visibility of the Back button
				SystemNavigationManager.GetForCurrentView().BackRequested += OnBackRequested;

				SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
					rootFrame.CanGoBack ?
						AppViewBackButtonVisibility.Visible :
						AppViewBackButtonVisibility.Collapsed;
			}

			if (e.PrelaunchActivated == false)
			{
				if (rootFrame.Content == null)
				{
					// When the navigation stack isn't restored navigate to the first page,
					// configuring the new page by passing required information as a navigation
					// parameter
					rootFrame.Navigate(typeof(MainPage), e.Arguments);
				}
				// Ensure the current window is active
				Window.Current.Activate();
			}
		}

		private void OnBackRequested(object sender, BackRequestedEventArgs e)
		{
			Frame rootFrame = Window.Current.Content as Frame;

			if (rootFrame.CanGoBack)
			{
				e.Handled = true;
				rootFrame.GoBack();
			}
		}

		private void OnNavigated(object sender, NavigationEventArgs e)
		{
			// Each time a navigation event occurs, update the Back button's visibility
			SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility =
				((Frame)sender).CanGoBack ?
					AppViewBackButtonVisibility.Visible :
					AppViewBackButtonVisibility.Collapsed;
		}

		/// <summary>
		/// Invoked when Navigation to a certain page fails
		/// </summary>
		/// <param name="sender">The Frame which failed navigation</param>
		/// <param name="e">Details about the navigation failure</param>
		void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
		{
			throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
		}

		/// <summary>
		/// Invoked when application execution is being suspended.  Application state is saved
		/// without knowing whether the application will be terminated or resumed with the contents
		/// of memory still intact.
		/// </summary>
		/// <param name="sender">The source of the suspend request.</param>
		/// <param name="e">Details about the suspend request.</param>
		private void OnSuspending(object sender, SuspendingEventArgs e)
		{
			var deferral = e.SuspendingOperation.GetDeferral();
			//TODO: Save application state and stop any background activity
			deferral.Complete();
		}
	}
}
